Stringed musical instrument



Nov. 13, 1951 J w MCBRIDE 2,574,881

STRINGED MUSICAL INSTRUMENT Filed Aug. 15, 1949 5 Sheets-Sheet l hN. MN.

bN. MN.

- 1N VEN TOR. JOHN w. M5QIOE FTTOQA/EV Nov. 13, 1951 J. w. MCBRIDE2,574,881

STRINGED MUSICAL INSTRUMENT Filed Aug. 15, 1949 5 Sheets-Sheet 2 POE m 6N7 r; m

INVENTOR. JOHN (U. M EQ/DE Nov. 13, '1951 ,j MCBRmE 2,574,881

STRINGED MUSICAL INSTRUMENT Filed Aug. 15, 1949 5 Sheets-Sheet 3 IllINVEN TOR. JOHN 0. M BP/DE HTTOENEV Nov. 13, 1951 J. w. M BRIDE STRINGEDMUSICAL INSTRUMENT 5 Sheets-Sheet 4 Filed Aug. 15, 1949 lam! JNVENTOR.ua/w w. MCBQ/DE Nov. 13, 1951 .1. w. M BRIDE STRINGED MUSICAL INSTRUMENTFild Aug. 15, 1949 5 Sheets-Sheet 5 I N V EN TOR. JOHN (1/- MBE/DEPatented Nov. 13, 1951 STRINGED MUSICAL INSTRUMENT John W. McBride,Burbank, Calif., assignor to Bantar, Incorporated, Burbank, Calif., acorporation of California Application August 15, 1949, Serial No.110,263

20 Claims. 1

The present invention relates to musical instruments, and moreparticularly to musical instruments having one or more tensioned stringsadapted to be vibrated. Examples of such instruments are guitars, banjosand violins.

An object of the present invention is to provide improved stringedmusical instruments embodying one or more movable frets capable of beingshifted bodily along the string, preferably with a rolling motion.

Another object of the invention is to create more than a single tone ona single tensioned string at the same time by bodily moving a fret alongthe string, preferably with a rolling motion. In this manner, harmonicscan be added to the fundamental tone.

A further object of the invention is to create more than a single toneon a single tensioned string at the same time by bodily translating aplurality of movable frets along the strings,

preferably with a rolling motion.

Yet another object of the invention is to provide for the creation of apredetermined harmonic emanating from a tensioned string in relation tothe fundamental tone or free vibrating length of the string.

Still a further object of the invention is to provide a musicalinstrument embodying a string stretcher arrangement that can bemanipulated easily and conveniently by the player with the same hand asthe player employs to shift a movable fret engaging the string.

A further object of the invention is to provide a musical instrumentembodying a depressible bridge arrangement which maintains propercontact with the string despite changes in the free vibrating length ofthe string.

Another object of the invention is to provide a light, movable fret thatcan be shifted bodily along the string of a musical instrument, and yetbe backed solidly so as to increase the duration of the tone emanatingfrom the string.

A further object of the invention is to provide a stringed musicalinstrument in which a metallic fret can be shifted along an attractingguide, and in which the string or strings of the instrument are utilizedto reduce, or offset partially, the attractive force of the guide uponthe fret, thereby facilitating shifting of the fret along the string,while maintainin its proper engagement with the string.

Another object of the invention is to provide improved devices forshifting and guiding one or more movable frets along a tensioned string,and for maintaining the proper relationship between the one or morefrets and the string.

This invention possesses many other advantages, and has other objectswhich may be made more clearly apparent from a consideration of severalforms in which it may be embodied. Such forms are shown in the drawingsaccompanying and formin part of the present specification. These formswill now be described in detail, illustrating the general principles ofthe invention; but it is to be understood that such detailed descriptionis not to be taken in a limiting sense, since the scope of the inventionis best defined by the appended claims.

Referring to the drawings:

Figure 1 is a top plan view of a musical instrument embodying theinvention;

Fig. 2 is a side elevation of the instrument;

Fig. 3 is a partial longitudinal section, on an enlarged scale, takenalong the line 3-3 on Fig. 1;

Fig. 4 is an enlarged cross-section taken along the line 4-4 on Fig. 1;

Fig. 5 is a top plan view, on an enlarged scale, of the depressiblebridge or harmonic bar portion of the instrument;

Fig. 6 is a section taken alon the line 6-6 on Fig. 7;

Fig. 7 is a section taken long the line 1-1 on Fig. 5;

Fig. 8 is a top plan view, on an enlarged scale, of the string stretcherportion of the instrument;

Fig. 9 is a section taken along the line 9-9 on Fi 8;

Fig. 10 is a somewhat diagrammatic side elevation of a modified form ofthe invention;

Fig. 11 is a cross-section through a portion of another embodiment ofthe invention;

Fig. 12 is a partial top plan view of the instru-' ment illustrated inFig. 11;

Fig. 13 is a cross-section, partly in elevation, of still another formof the invention;

Fig. 14 is a partial longitudinal section through another embodiment ofthe invention;

Fig. 15 is a cross-section taken along the line l5-I5 on Fig. 14;

Fig. 16 is a top plan view of the instrument disclosed in Fig. 14, theportion disclosed in Fig. 16' representing an extension of Fig. [4 tothe right thereof;

Fig. 17 is an enlarged cross-section taken along the line l1|1 on Fig.16;

Fig. 18 is an enlarged longitudinal section taken along the line I 8-! 8on Fig. 16.

The instrument disclosed in Figs. 1 to 9, inclusive, includes a bodymember ID having a string anchoring portion H at one end, and a pegboard portion l2 at its other end. Arranged transversely across theupper surface of the body momher is a bridge l3 having spaced notches 14for the reception of tensioned strings 15, that are to be placedselectively in vibration. The strings pass through these notches l4 andthrough other notches IE5 at the rear of the bridge to a positiontherebelow, the strings are suitably secured or anchored, in awell-known manner.

From the anchor end of the instrument, the

strings are disposed lengthwise along the upper portion of the bodymember toward the inclined peg board 12, the strings I passing throughnotches 11 in a pair of spaced bridges I8, 19 in the peg board, and thenbeing secured to the usual tuning posts 20 in the latter, which may berotated, in a known manner, by the pegs 2|. Tightening of the pegs 21will serve to stretch the strings [5 between the bridge members [3, l3,and determine the initial tension in the strings, which may be tuned asdesired.

Twosets 'of strings are disclosed in the drawings, although it is to beunderstood that one or. more sets can be employed, each set includingoneor more strings. Inasmuch as the mechanism for determining the freevibrating length of the strings is essentially the same, a detaileddescription of the operating mechanism for one set will suifice for all.

The free vibrating length of each string i5 is determined by shifting aroller assembly or fret 22 lengthwise'along the string, the rollerassembly axis being transverse, and preferably at right angles, to thedirection in which the strings extend. Each roller assembly includes anintermediate string roller 23 rotatable on a shaft 24 that is fixed toguide rollers 25 on opposite ends thereof. Each guide roller has anintermediate flange 23 for precluding" substantial movement of theroller assembly endwise of its axis. The string roller 23 is disposedunder a set of strings I5, and engages all strings in such set, exertingan upward force thereon. The guide rollers 25 engage inclined guidingsurfaces 21 that are disposed under the strings. These surfaces arepreferably formed in helical fashion, and serve to feed each rollerassembly 22 back and forth along the strings l5, in a manner to bedescribed hereinafter.

: The helical guide mechanism is disposed in'a recess 23'in the bodymember H3, and extends between the anchor end I l and peg board end I2of the latter. A-shaft or spindle is fixed to the body member ID, as bybeing welded or otherwise secured to a metallic plate 33 extendingtransversely across the body member and secured to'the latter.A'transverse outer endplate 3| is rotatably mounted on this spindle, aswell as a transverse inner end plate 32. The outer plate 3| is securedto a helical guide 33'that extends along and under the strings l5, inthe same manner as a helical thread of relatively steep pitch or lead.This outer helical guide 33 may be cut from a tubular member to providea pair of helical guiding surfaces 21 that are substantially 180 degreesout of phase.

5,; In;a similar manner, the inner plate 32 is secured to an innerhelical guide member'34 disposed within the outer guide 33 and providedwith helical surfaces 21 substantially 180 degrees out of-phjaseivvithrespect to each other, but having the same pitch or lead. These innerhelical surfaces. however, are of the opposite hand from the directionof inclination of the outer guide surfaces 21.

Theouter helical guide member 33 extends towardthe inclined peg board12.; where it is secured to an end plate 35 fixed to an outer of tubularshaft 35. In a similar manner, the inner helical guide member 34 issecured to an end plate 31 fixed to an inner shaft 38 extendingcompletely through the outer shaft 36, and also through a stationaryplate 39 to a location within the peg portion 12. The end of this shaft38 is attached to a helical spring 40, the outer end of the spring beingattached to the shaft supporting member 39.

The inner helical guide member 34, as noted above, is wound with anopposite hand from the outer guide member 33. That is, one of the guidemembers may have helical surfaces 21 equivalent to a steeply pitchedleft-hand helical thread, whereas the other guide member surfaces areequivalent to a steeply pitched righthand helical thread. These helicalguiding surfaces 21 engage the guide roller portions 25 of the rollerassembly and cradle the latter therebetween. As an example, the guideroller 25 on one end of the roller shaft 26wil1 engage the outer helicalsurface 21 at one side of a vertical plane through the roller axis, andthis same guide roller 25 will alsoengage the inner'helical guidesurface 21 on anotherside of such plane, providing a spaced two-pointsupport for the guide roller on opposite sides of its vertical centralplane. In like manner, the guide roller 25 on the other end of theroller shaft 26 will engage an outer guide surface and also an innerguide surface 21 on opposite sides of a central vertical plane throughthe roller axis. In effect, the roller is cradled by the guides 33, 34,being held by the tensioned string -J5 in engagement with the helicalsurfaces 21, the latter surfaces reactively holding the-string rollerportion 23 of the assembly in firm engagement with the strings.

It has been stated that the helical guiding surfaces 21 on the-outerguiding member 33 are substantially degrees out of phase with respect toone another, and that this is true also of the helical surfaces 21 onthe inner guide member '34. Actually, the exact extent of these surfacesbeing out of phase depends upon the diameter of the guide rollerportions 25. The surfaces are out-of phase by an angular extent whichwill insure the disposition of the roller assembly axis at right anglesto the direction in which the tensioned strings extend.

Each roller-assembly 22 is prevented from moving endwise of its axis byproviding the flange 28 on each guide roller portion 25 extendingbetween the inner andouter helical members 33, 33 (see Fig. 4). It isapparent that such flanges 25 will engage the opposed surfaces of thehelical members and prevent substantial endwise movement of the rollerassembly.

Each roller assembly 22 is moved along the strings l5 by simultaneouslrotating the inner and outer-guides 34, 33 inopposite directions and bythe same angular extent. These guides are coaxial of each other,inasmuch'as the axis of the fixed spindle 29 is coaxial with the axis ofmounted in the body member 10 transversely of the shafts 36, 38, whereasthe other pinion 42 meshes with an upper rack 45 suitably secured to thesame key 44; y

It is apparent that movement of the key 44 by a persons fingers willmove the racks 43,45 longitudinally in the same direction. Since theyare engaging the pinions 4|, 42 on opposite sides of the common axis ofthe latter, the pinions will be rotated in opposite directions tocorrespondingly rotate the inner and outer helical guide members 34, 33in opposite directions.

Inward movement of the key 44 by the persons fingers is resisted by thehelical spring 40 so that removal of such force of movement causes theenergy stored in the spring to rotate the pinion 4| fixed to the shaft38 in the reverse direction, which correspondingly shifts the key 44 inthe reverse direction, and also the pinion 42 attached to the outershaft 36 in the reverse direction. It is, accordingly, apparent from theforegoing description that longitudinal movement of a key 44 will rotatethe helical guides 33, 34 in opposite directions. As the guides arerotated, they will shift the roller assembly 22 longitudinally of thestrings l5, the parts being so related that a roller assembly may beshifted to thedesired longitudinal extent along the strings.

The guide rollers 25 at all times have a fourpoint contact with thehelical guiding surfaces 21, which positively convey the assembly 22along the strings l5, and also hold it in proper assembled relation withrespect to the strings. In view of the fact that the string rollerportion 23 of the assembly is rotatable on the shaft 25, movement of theassembly along the strings can occur with the string roller portionrolling under and in contact with the strings without any slidingfriction, thus insuring the smooth operation of the device, with aminimum of extraneous noise.

A plurality of sets of strings l and roller assemblies 22, andassociated mechanisms is disclosed. Each set has its rack and pinion andreturn spring devices, which is the same as the arrangement shown mostclearly in Fig. 3. Of course, the racks 43, 44 on the keys 44 are solocated and arranged thereon as to engage with only 'a single set ofcoaxial pinions M, 42, each key being effective for accomplishing bodilytranslation of only a single roller assembly 22 along a set of strings.

For the purpose of introducing a harmonic into the vibrating string, adepressible bridge 48 is disposed at the key end of the instrument. Adepressible bridge or harmonic bar 49 is disposed under each set ofstrings I5, and may be arranged either at right angles thereto, or itmay be disposed obliquely with respect to the strings. Each harmonic bar45 is threaded onto a rod 55 which is secured to an arm 5! pivotallymounted on a hinge pin 52 extending through all the depressible bridgearms 5|. The pin 52 is supported by brackets 53 attached to theinstrument body. A coil spring 54 is disposed around the hinge pin 52within each arm 5|, one end of the spring bearing against the body orsupporting member H3, and the other end against the pivoted arm 5!, forthe purpose of urging the arm and the harmonic bar 49 upward- 1y,causing the bar to engage the strings [5 in each set in the manner of abridge. The point of such engagement may be predetermined or varied,prior to assembly of the depressible bridge device, by suitablythreading the bar 49 on the rod 50.

As the instrument is being played, and the free vibrating length oi.each string varied by suitable manipulation of a key 44, and rolling ofeach roller assembly 22 along the string IS, the spring 54 urges thedepressible bridge bar 49 into proper contact with the string,maintaining such proper contact despite movements of the roller assembly22 along the string. Because of the presence of the depressible bridge48, harmonics are introduced into the sound emanating from the vibratingstring, the particular harmonic effect being dependent on the freevibrating length of the string between the depressible bridge 48 and theparticular position of the roller assembly 22 along the string i5. Thesetting of the string into vibration, by plucking or picking it betweenthe roller assembly 22 and the bridge [3 at the anchor end of theinstrument, will also set the string into vibration between the rollerassembly 22 and the depressible bridge 48.

If desired, the tuning of the individual strings of the instrument canbe changed conveniently by the operator. Also, pitch tremolo or vibratocan be imparted to the string. To accomplish these purposes, a stringstretcher device 56 is disposed adjacent the keys 44. This stringstretcher device includes sets of keys 51 mounted on the ends of arms58, that are rotatable on rods 59 secured to the bottom plate 60 of thelongitudinally spaced fixed bridge members [8, l9 across which thestrings extend. The inner end of each arm 58 has an upwardly projectingfinger 5i adapted to engage a string 15. When a key 51 is depressed, thefinger El urges the string i5 laterally between the fixed bridge members18, I9 and can increase its tension.

As disclosed most clearly in Figs. 8 and 9, an outer set of keys 5'! isassociated with two of the three strings in one set, and an inner set ofkeys 57a is associated with two of the three strings in the other set.During playing of the instrument, the persons fingers can readilydepress or vibrate one or more of the keys 5?, 51a to vary the tensionin the strings l5 with which such keys are associated, thus momentarilychanging the tuning of the individual string. Proper manipulation ofeach key 57 or 57a also makes it possible to impart a vibrato or pitchtremolo to the string.

As has been noted, the same hand of the person can be used to operatethe keys 44 for shifting the roller assemblies 22 along the strings E5,and also for simultaneously manipulating the string stretcher device 56.

In the form of invention disclosed in Fig. 10, two roller assemblies 22,22a are shifted along the helical guides 33, 34a, and, in addition,these guides are made with a varying pitch along their lengths. Oneroller assembly 22a is disposed under one or more tensioned strings i5,and is in engagement with the helical surfaces of the inner and outerguide members. A second roller assembly 22 is disposed ahead of thefirst roller assembly, and is cradled on the guides 33a, 34a, anddisposed in contact with the strings i5, in essentially the same manner.

The pitch of both inner and outer helical guide members 33a, 34adecreases from one end to the other, from which it is apparent thatrotation of the helical guide members in opposite directions will bodilytranslate the pair of rollers 22, 22a, along the string [5, the leftroller 22a being moved a greater distance than the right roller 22. Thatis, assuming the rollers 22, 22a to occupy the initial positionsindicated in full lines in Fig. 10, and the guides rotated to shift therollers toward the right to the dotted line positions, the rear roller22a will tend to approach or catch up to the forward roller 22.Conversely, rotation of the helical guides 33a, 34a in the oppositedirection will cause the rear roller 22ato recede from the forwardroller 22.

The two rollers 22, 2211 are used to introduce harmonics into thevibrating string l5. Actually, the string has two free vibratinglengths, one between the forward roller 22 and thebridge 13 at theanchor end of the body, and the other the length between the rollers 22,22a themselves. Thus, the stringmay be set in vibration, the frequencyof vibration imparted to the string b.e.

causeof the free vibrating length between the rollers beingsubstantially higher than the :frequency of Vibration .imparted to thestring due to the free vibrating length between the forward roller '22and the bridge i3.

The thread pitch of the guides is chosen soas to decrease along thelength of the latter, and two rollers may be used to obtain a set,predetermined harmonic relation to the free vibrating length of thestring as the two rollers 22, 22a move along the string. It is apparentthat the free vibrating length of the string between the forward roller22 and bridge i3 is decreasing as the forward roller approaches thebridge [3. At the same time, the free vibrating length of the stringbetween the rollers 22, 22a themselves is also decreasing. Thus, theratio of the harmonics between the two free vibrating lengths of thestring remains substantially constant. The desired ratio can bepredetermined, and the pitch of the helical guides designed and variedaccordingly.

In the form of invention shown in Figs. 1,1 and 12 a pair of spacedrollers l6, H is used and is shifted along the strings if: to accomplishthe same general purposes as is accomplished in the embodimentillustrated in Fig. 10. However, the rollers it, ll may be independentlyadjusted along the strings [5 so as to vary their free vibratinglengths.

As illustrated, forward and rearwardrollable frets or roller assembliesill, T2 are disclosed. The forward roller assembly includes anintermediate guide roller portion 12 and end guide roller portions 13secured to a shaft 14. String roller portions ?5 are rotatably mountedon the shaft it between the intermediate guide roller and the end guiderollers, these-string roller portions being disposed under and engaging.a plurality of tensioned strings i5. .Dispose'd below the assembly 'iil:is a pair of laterally spacedhelical guides it whose marginal surfacesis! engage the peripheries of the guide rollers 12,13. Thus, the sideedges or helical guiding surfaces "H of one guide member 75 are incontact with the intermediate guide roller 12 and one .of :the endrollers 13, whereas thesideedgesor helical guiding surfaces of the otherguide member 16 are en agement with the intermediate uide roller 12 andthe other end guide roller 13. Lateral displacement of the rollerassembly along its axis is prevented by providing a central peripheralflange 7.8 on the intermediate guide roller .?.2 which may contact theopposedside edges of the helical guide members 1.6.

The guide members 76 have the .same pitch of the same hand. They arerotated about their parallel axis simultaneously in the same .directionto create bodily translation of the roller assembly it along thetensioned strings .15. .Such roe tation is accomplished 'by securingeach guide to a :pinion 79, both pinions :meshing with zasingle rack 80attached't0'a key 8!. By slidingthekey transversely of the strings, thepinions 1.9 are caused to rotate, which, in turn, rotate theqhele calguide members ,19 and feed the roll r assemy in along the tensi ned s riThe. rearward roller ass mbly H is f lesser extent than the forw r sembly 10. I cludes a central shaft 82 on which the end guide rollers 83are secured. and o w c e inter mediat strine rol er p rtion 84 i a b f rengaging the tensioned strings IS. The end rolls ers B3 are disposedupon vhelical guides 85 of the same pitch and havin g id g urfa s 86 ofhe s m hand. which pitc may b e ame r dif ferent from the pitch of theinner guide members l6. Endwise movement of the rearward roller assemblyH along its axis is prevented by p ovidin an n e nge 81 011 e ch u deroller portion which is adapted to engage the side edge of an outerhelical guide member 85. V 7 V The outer helical guides 85 may berotated simultaneously about their parallel axes in a manner similar tothe helical guides 75. A pinion 88 may be secured to the end of eachouter guide 85 meshing with a common rack 89 fixed to a slidable key 90.Depression of the key 98 will roev tate the helical guides 85 in thesame direction, and feed the rearward roller 1! along the tensionedstrings I5.

By suitable manipulation of the ke ys 8|, .96, the rearward and forwardrollers I, it! may be shift: ed with respect to each other and withrespect to the tensioned strings l5. One roller, such as the forwardroller assembly Ill, .can be utilized to provide the fundamental tone,wherea .theother roller, such as the rearward roller H, may be shiftedwith respect to and independently of the forward roller, to provide thedesired harmonic or partial.

In Fig. 13, a magnetic roller assembly is disclosed which is essentiallythe same as the rearward roller assembly H shown in Figs. 11 and .12,insofar as the helical guide arrangement 85g, and the manner of rotatingthese guides to feed the roller assembly Ha alonetensioned strings I5 isconcerned. However, the magnetic -r-O1ler assembly Ha shown in Fig. 13could be constirtuted by a solid roller throughout its length, or itcould be a divided roller, as the ther fo ms of the invention.

The guide portions 83a. of the magnetic roller assembly engage magnetichelical guide members 85a which attract .it and hold it in .a 'dDWn-vward direction against the strings 15, which may be disposed below themagn ti rol e asmuch as the strings need not .be relied upon to hold theroller Ha in .proper engagement withthe helical guides 85a. By suitablymanipulati g the key and rotating the pinions .88, the helical guides85a are caused to rotate with assurance that themagnetic roller Ha .willremain in con.- tact therewith as it is translated bodily, with rollingmotion, along thestrings l5. .As indicated above, the roller Ha. can .bemade solid, since the strings 15 are disposed on the same s de Of theroller as the helical guides 85a.

The dispositionof the tensioned-strings [5111clow, or on the same sideof, the roller as the helical guides 85a. causes the tension in thestrings 1.5 .to reduce the pattractiveforce of the roller 1?; La againstthe guides. As a result, it is easier to shift .the roller along .theguides; making the ;in-. strument operable with greater facility and dexterity by the musician.

In .addition, the :magnetic attraction ;betwee :theguides 85a.andlroller J lazgivesasolidib'acking to the roller, and thus increasesthe duration of the tone emanating from the string or strings I5.

Of course, the forward roller I shown in Figs. 11 and 12 could also bemade magnetic and engageable with magnetic guides, so as to possess thesame attributes as the rearward roller Ila disclosed in Fig. 13.

In view of the attractive force between the magnetic roller Ma and theguide 85a, the roller may be made of light weight and still be heldsolidly and in engagement with the guides. Here again, the light weightreduces the inertia forces tending to resist rapid traverse of theroller fret IIa along the strings I5.

Another form of invention is disclosed in Figs. 14 to 18, inclusive, inwhich one or a plurality of rollers may be shifted selectively along oneor more tensioned strings. In this form, four rotatable helical guidemembers 95, 96, 91, 98 are disclosed. Each guide member has a helicalguiding surface 99 adapted to engage a part of a roller assembly I00 orIOI.

The outermost guide member 95 is secured to an end arm I02 fixed to ashaft I93 rotatable in a supporting frame I04 and having a pinion Iattached thereto meshing with an upper rack I06 of a key I01 slidable ina stationary guideway I08. The next helical guide member 96 is rotatablewithin the first guide member 95, being secured to a hollow shaft I09rotatable within the outer shaft I03, and having a pinion II 0 fixed toit adjacent the first pinion I05 and meshing with a lower rack IIIattached to the slidable key I01.

By reciprocating the key I01, the pinions I05, I I0 are rotated inopposite directions to rotate the helical guides 95, 96 in oppositedirections. These guides, as will be explained hereinafter, cooperatewith a forward roller assembly I JI, that is adapted to contact one or aplurality of tensioned strings I5.

A third helical guide 98 is mounted for rotation within the second guide96, and is fixed to a third hollow shaft II2 rotatable within the secondshaft I09. A pinion I I3 is fixed to this third shaft and meshes with anupper rack II4 attached to a second key I I5 slidably supported in aguideway I I6. A fourth innermost helical guide 91 is rotatable withinthe third guide 93, and is secured to an arm I I1 fastened on a shaftII8 extending through the third hollow shaft II2. A pinion II 9 issecured to the innermost shaft I I8 and meshes with a lower rack I20 onthe second key I I5.

A helical spring I2I is secured to the first pinion I05 and to thesupporting frame I04 for returning the outermost helical guides 95, 96toward their initial positions following depression of the key I0I.Similarly, a helical spring I22 is secured to the innermost shaft I I8and the frame I04 for returning the two inner helical guides 97. 98toward their initial positions following release of the depressibleforce on the second key II5.

By virtue of the rack and pinion arrangements, the first key I07 willrotate the two outer helical guides 95, 96 equally in oppositedirections,

whereas the second key II5 will rotate the inner two helical guides 91,98 in opposite directions. The outer two guides 95, 96 are of equalpitch, although of opposite hand, which is also true of the inner twoguides 91, 98.

The inner two guides 91, 98 serve to translate a roller assembly or fretI00 along the tensioned strings l5. This assembly includ s a g rally-U-shaped supporting bracket I 23, whose upwardly extending arms I24carry a roller I 25 which is in engagement with the tensioned stringsI5. The base of the bracket I23 is attached to a mounting member I26extending at right angles to the axis of the string engaging roller I25and on opposite sides of the roller. A vertical depending shaft I2? issecured to each end Of the mounting member I26, each shaft carrying anupper guide roller I28 and a lower guide roller I29, that can rotaterelative to each other upon the vertical shaft I2'i. The upper guideroller I28, on one side of the string roller I25, engages a helicalguiding surface on one side of the third guide member 98, whereas thelower guide roller I29 engages the helical surface I3I of the innermostor fourth rotatable guide member 91. These rollers I29, I29 aremaintained in proper relation with respect to the guides 98, 91, and areprevented from dropping with respect thereto by spaced flanges I32 oneach roller engaging the top and bottom sides of the guides 98, 97.

As disclosed in Fig. 17, the rollers I28, I29 engage the third andfourth guides 91, 98 adjacent their crossing point, which will besubstantially under the string roller I25. A similar forward pair ofvertically arranged rollers 128a, I29a engages the third and fourthhelical members 91, 98 contacting their helical guiding side edges I30a,I3 Ia on opposite sides from the edges that are contacted by therearward pair of rollers I28, I29 previously described. The forwardrollers I28a, I29a also have the flanges I32 engaging the helical guidemembers, and cooperate with the flanges I32 of the other roller membersI25, I29 to support the entire roller assembly I 00 in proper relationwith respect to the strings I5.

When the two inner helical guide member 91, 98 are rotated uponreciprocation of the second key I I5, they operate upon the verticallydisposed rollers I28, I29, I28a, I 29a to shift the roller assembly I00lengthwise of the strings I5. The upper and lower rollers I28, I 28a andI29, I29a will rotate in opposite directions during such movement, sincethe companion helical guiding surfaces with which they engage effecttheir rotation in the manner described. During their movement along thehelical guiding surfaces I30, I30a, I3 I, I 3 la, they will shift therolling fret I00 along and in contact with the tensioned strings I5without any sliding friction against the strings.

The forward roller assembly IOI is designed to cooperate with the twoouter helical guiding members 95, 96. This roller assembly has asupporting bracket I40, with a string roller I4I rotatable in theupwardly extending bracket arms I42 and contacting the tensioned stringsI 5. Vertically disposed and laterally spaced shafts I 43 depend fromthe base I44 of the bracket, each shaft carrying a roller I45 which isadapted to contact the outer helical guide portions I46, I41 of thehelical guide members 95, 96. As seen in Fig. 18, the upper rollerportion I45a on one side of the point of intersection of the helicalguides engages the outermost guide surface I 46, whereas the lowerroller portion I452) engages the helical surface I 46 of the secondguide member 96. The other vertical roller device I450 engages the sametwo guides 95, 96 on the opposite side of their crossing point.-

In view of the manner in which the rollers I45, I450 and the guidesurfaces I46, I 41 are related to one another, the roller portions I45a,I45b may be secured together for simultaneous rotation in the samedirection, since the oppositely moving:

helical guide members 95, 96 tend to rotate the rollers MEa, [55 in thesame direction This is true oiboth vertical rollers I 35, 450 onopposite sides of the crossing point of the guides 95; 96.

To holdthe roller assembly in proper position, each roller device I45,H350 may be provided with spaced flanges rec engaging the upper andlower surfaces of the. rotatable guide members 95, 95.

Since the outermost guide 95 has a greater radius of rotation than theinner guide 96 adjacent it, the upper roller I450; will have a largerdiameter than the lower roller portion [45b so that the guides 95, 96rotate both upper and lower roller portions! 45a, l45b the same angularextent.

Movement of the first key ID! will rotate the two outer helical guides95, 96 in opposite directions'and: will shift. the forward roller lillalong the'strings I51 The forward and rearward rollers MI; maybe usedseparately, or they may be used together, being suitably moved along thesame strings by appropriate manipulation of the keys" N31,. H5. Onerollensuch as the forward roller I01, can. provide the fundamentalfrequency, whereas the other roller, such as the rearward roller we, canbe manipulated to provide 'thedesired harmonic or partial.

The inventor claims:

I. In a stringed musical instrument: a ten sioned string; a first memberin contact with said string; a rotatable member having an inclinedguiding surfacethereon engaging said first member to'bodily translatesaid first member along the string upon rotation oi'said rotatablememher; and a second mov'able' member engaging said string intermediateits tensioned length to one side of said-first member.

2. In a stringed musical instrument: a tensioned string; longitudinallyspaced first and second members in contact with said string; a rotatablemember disposed lengthwise of said string; saidrotatabl'e member havinga helical guiding surface thereon engaging said first and second membersto bodily translate said first and second members along the string'uponrotationvof saidrotatable member.

3. In a stringed musical instrument: a tensioned string; a pluralityoflongitudinally spaced members in contact with saidstring; one or'morerotatable members. disposed lengthwise of said string; said one ormore'rotatable members having one or more inclined guiding surfaces"thereon engaging said spaced members to bodily translate said spacedmembers along the string upon rotation of said one or more-rotatablemembers;

4- In a stringed musical instrument: a tensioned'string; a plurality oflongitudinally spaced roller members in contact with said string; one ormore rotatable members disposed lengthwise of said string; said one ormore rotatable members having one or more inclined guiding surfacesthereon engaging said rollers'to bodily translate said-rollers along thestring upon rotation of'said one orv more rotatable members;

5. In a stringed musical instrument: a ten'- sinned string; a pluralityof longitudinally spaced rollers in contact with the string; one or morerotatable members disposed lengthwise of said string; said one or morerotatable members having: one or'more 'inclinedguiding surfaces thereonengaging said rollers to bodily translate said rollers along the string.upon rotation'of said one or'more rotatable members and means forrotating; said one or more rotatable members to bodily translate saidrollers simultaneously along the string.

6; In a stringed musical instrument: a. tensioned string; a roller incontact with the string; means -for translating said roller bodily alongthe string to vary the free vibrating length of the string; anothermember engaging saidstring to one side of said roller; and resilientyieldable means constantly urging said other member into engagement withsaid string.

"7. In a. stringed musical instrument: a tensioned string; a member incontact with the string; means for translating'said member bodily alongthe string to vary th free vibrating length of the string, comprisingmanually manipulative instrumentalities; and means adjacent saidmanually manipulative instrumentalities and selectively engageable withsaid string for changing the. tension of said string, said tensionchanging means being operable by the hand of a personsimultaneously-with engagement of such persons hand with the manuallymanipulative instrumentalities.

8. In a stringed musical instrument: a tensioned string; first andsecond, longitudinally spaced. members in contact with said string; arotatable member disposed lengthwise of said string and having aninclined guiding surface thereon engaging said. second member to bodilytranslate said second member along the string upon rotation ofsaidanother rotatable member; and means for rotating said rotatable members.

9. In a. stringed musical instrument: a tensioned string; a magneticmember in contact with said string; and meansin attractive relation withsaid magnetic member for translating said magnetic member bodily alongthe string to vary the free vibrating length of .the string.

10. Ina stringed musical. instrument: a tensioned string; a magneticroller member in contact with said string; a rotatable member disposedlengthwise of said. string; said rotatable member having a helical.guiding surface thereon in attractive engagement with said magneticmember to bodily translate saidmagnetic member. alongthe string uponrotation of said rotatable member.

11. Ina stringed musical instrument: a tensioned string; a magneticroller member disposed K sioned string; a plurality of longitudinallyspaced roller members incontact with said string; a rotatable memberdisposed lengthwise of said string; said rotatable member having ahelical guiding surface thereon of varying pitch engaging said rollermembers to bodily translate said roller members simultaneously along thestring uponrotation of said rotatable member.

13. In a stringed musical instrument: a' ten-a sioned string; aplurality of longitudinallyspaced roller members in contaotwith saidstring; a first rotatable member; a second rotatable member" locatedwithin said first member; said rotatable members having helicalguidingsurfaces thereon engaging said roller members, the helicalsurface of said first member being of the opposite hand from the helicalsurface of said second member,

said helical surfaces of said rotatable members being of varying pitchalong the length of the string; and means for rotating said rotatable 13members simultaneously in opposite directions to translate said rollermembers bodily unequal distances along said string.

14. In a stringed musical instrument: a tensioned string; first andsecond longitudinally spaced members in contact with said string; aplurality of first rotatable members disposed lengthwise of said stringand having helical guiding surfaces thereon engaging said first memberto bodily translate said first member along the string upon rotation ofsaid first rotatable members; a plurality of second rotatable membersdisposed lengthwise of said string and having helical guiding surfacesthereon engaging said second member to bodily translate said secondmember along the string upon rotation of said second rotatable members;and means for rotating said rotatable members.

15. In a stringed musical instrument: a tensioned string; first andsecond longitudinally spaced roller members in contact with said string;a plurality of rotatable inner members disposed lengthwise of saidstring and having helical guiding surfaces thereon engaging said firstroller member to bodily translate said first roller member along thestring upon rotation of said inner members; a plurality of rotatablemembers disposed laterally outwardly of said inner members andlengthwise of said string and having helical guiding surfaces thereonengaging said second roller member to bodily translate said secondroller member along the string upon rotation of said outer rotatablemember; and means for rotating said inner and outer members.

16. In a stringed musical instrument: a tensioned string; a rotatablemember disposed lengthwise of said string and having a helical guidingsurface thereon; a bodily translatable device, said device including afirst rollable element in contact with said string, and one or moreother rollable elements in engagement with said helical guiding surfaceto effect bodily translation of said device along said string uponrotation of said rotatable member, the axis of rotation of said one ormore rollable elements being disposed at an angle to the axis ofrotation of said string contacting rollable element.

17. In a stringed musical instrument: a tensioned string; first andsecond longitudinally spaced members in contact with said string; a pairof rotatable members disposed lengthwise of said string and havingguiding surfaces thereon inclined in opposite directions and engagingsaid first member to bodily translate said first member along the stringupon rotation of said rotati4 able members in opposite directions; apair of second rotatable members disposed lengthwise of said string andhaving guiding surfaces thereon inclined in opposite directions andengaging said second member to bodily translate said second member alongthe string upon rotation of said second rotatable members in oppositedirections; and means for rotating said rotatable members.

18. In a stringed musical instrument: a tensioned string secured to saidinstrument at both ends of said string; a movable member in contact withthe string; means for translating said member bodily along the string tovary the free vibrating length of said string between said member andone end of said string; and means providing a projection movabletransverse to said string selectively to engage said string on that sideof said movable member remote from said one end to vary the tensionthereof.

19. In a stringed musical instrument: a tensioned string; first andsecond longitudinally spaced movable members in contact with saidstring; a first pair of rotatable members having inclined guidingsurfaces thereon in engagement with said first member bodily totranslate said first member along said string upon rotation of saidfirst pair of rotatable members; a second pair of rotatable membersdisposed within said pair of rotatable members and having inclinedguiding surfaces thereon in engagement with said second member bodily totranslate said second member along said string upon rotation of saidsecond pair of rotatable members; means for rotating said first pair ofrotatable members; and means for rotating said second pair of rotatablemembers.

20. In a stringed musical instrument: a tensioned string; a plurality ofstring contacting members movable longitudinally of said string; amovable member having guiding surfaces thereon engaging said stringcontacting members bodily to translate said string contacting membersalong said string upon movement thereof; and means for moving saidmovable member.

JOHN W. MoBRIDE.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number

